1. Field of the Invention
The present invention relates generally to suspension systems for shock absorption. More specifically, the present invention relates to systems and methods to for limiting shock in a disk drive head suspension assembly employing a multi-step shock limiter.
2. Related Art
A disk drive head suspension, or head gimbal assembly typically comprises a load beam and a flexure, the load beam extending longitudinally from a base plate, and the flexure moveably coupled to the load beam. A read/write head is typically mounted at or near the distal end of the flexure. The read/write head performs the functions of reading data from and writing data onto a disk surface. The minimum distance between the read/write head and the disk surface, also known as lift clearance, affects the operation of the read/write head and is therefore an important design parameter. Thus, disk drive suspensions are preloaded to maintain lift clearance at a desired distance. However, during a shock condition, vertical movement of the flexure may occur, causing the read/write head to impact the disk surface. This action may cause damage to the read/write head, load beam, or flexure, and permanently alter the lift clearance. In severe cases, the impact may damage the disk surface, causing loss of stored data. Shock conditions may result from normal operation, for example, during loading or unloading of a disk. Other sources of shock include non-operational phenomena such as shipping, handling, or installation that cause external jarring or impact to the system.
The current state of the art provides a limiter disposed between the flexure and the load beam to protect the flexure in the event of shock. Under shock conditions, the limiter contacts an engagement surface to dampen shock and prevent excessive damage to the suspension assembly components. However, the limiter itself is generally made of a metal such as stainless steel, and may also be made thinner than the engagement surface. Limiter rigidity is therefore a design concern, especially for short duration shock on the order of 0.5 milliseconds, which can fracture or otherwise deform the limiter. Consequently, the determining factor in the shock rating of the suspension system may depend entirely on the design of the limiter.
In view of the foregoing, there is an ongoing need to improve the performance of limiters in disk drive suspension systems.